View of the Eastshore Freeway in Berkeley, which is often clogged with cars. Image courtesy of Wikimedia user Minesweeper.

A transformational shift in perspective is taking shape in California, where the state's transportation agency, Caltrans, is in the midst of alterings its project impact analysis metrics by abandoning LOS in lieu of VMT.

Why is this important? Level of Service (LOS), on the one hand, measures the impact of a project on traffic flow in a given area, prioritizing the movement of cars over other factors. Because LOS is optimized for automobile traffic, project impact mitigation measures often favor reducing automobile congestion so that traffic can keep flowing. Common LOS-led responses to a high-impact projects include highway widening and the addition of new driving lanes, for example, approaches that often actually work to make traffic worse through the phenomenon of "induced demand."

Vehicle Miles Traveled (VMT), on the other hand, measures the amount of travel generated for all vehicles by a given project. For projects that are measured against VMT, the goal shifts from reducing congestion to reducing the amount of travel that needs to take place, overall. That approach favors infill development as well as densification and mixed-use development, in addition to also promoting "active transportation" modes like pedestrianism and bicycling.

Streetsblogreports that the department is beginning to develop guidance embracing the shift in response to the SB 743 law passed in 2013 compelling the state to re-evaulate how it measures the environmental impacts of development. According to Streetsblog, the change could go into effect as soon as spring or summer of 2020.

The new approach by Caltrans means that California may begin to make headways in terms of reducing its sprawl through infill development and other approaches. The state's sprawling character is one reason carbon emissions generated by the transportation sector remain persistently high while impressive progress is made on other fronts like energy generation and building performance.